In those situations where temperature extremes may impair the operation of an antenna system, it is necessary to completely characterize the parameters of the system by testing it over its operational temperature range. Large walk in thermal test chambers are well known for testing the performance of electronic components and systems over a temperature range. To provide insulation from the surrounding ambient atmosphere, these prior art test chambers are constructed of insulated metallic walls. But the metallic walls render these prior art systems unacceptable for testing antenna characteristics over a temperature range due to the reflection and absorption of incoming and outgoing RF signals by the metal walls. For example, it is necessary to conclusively demonstrate the ability of a movable dish antenna to track a distant non-stationary terminal over a wide temperature range. To perform this test the ground based antenna terminal must be placed in a thermally-insulated chamber in the far field of the incoming (or out-going) signal from the non-stationary terminal. During the test the dish antenna is moved to track the non-stationary terminal. It is impossible to perform such a test in the prior art test chambers due to the reflection and attenuation of the signals caused by the metallic walls.
The only known prior art technique for directly demonstrating the operation of these radio links is to locate the antenna system within an enclosure and behind a plexiglass window, so the RF energy propagates through the window. This technique does not provide the necessary thermal insulation to test the antenna over large deviations from ambient temperature. Indirect test methods include hand-wiring the radio link between the antenna system and the distant terminal to demonstrate system performance. But, this prior art technique is not acceptable because it substitutes a hard-wired link for the radio link that is undergoing testing. It is also known to analyze system performance at a given temperature and extrapolate its performance over the expected operational temperature range. This too, may introduce unforseen errors into the test results.